First image with the CfA superconductive HEB receiver: The protostellar outflow from IRAS 20126+4104 in CO (J=7-6)

We present a spectral line image in CO (J = 7-6) of the spatially compact m olecular outflow from the massive protostar IRAS 20126+4014, observed using a novel superconductive hot-electron bolometer (HEB) heterodyne receiver w e recently installed at the 10 m Heinrich Hertz Telescope. The bipolar outf low is clearly detected and resolved with a center of symmetry situated at the position of the massive protostar, previously identified as an IRAS sou rce and a millimeter continuum source. The peaks of the emission from the r ed- and blueshifted CO lobes are separated by approximate to 14 " (0.1 pc), and the velocity of the CO emission extends +/-30 km s(-1) from the ambien t cloud velocity. The total outflowing gas mass is approximately 4 M., whil e the outflow rate is at least 6 x 10(-4) M. yr(-1). Both high-velocity CO emission maxima trail the NH3 (3, 3) and SiO clumps located 3 "-4 " downstr eam (farther from the IR source) in the flow. The high-excitation CO line a nd the NH3 are likely tracing the heated gas entrained in different parts o f the bow shocks. By interpreting our observations in terms of a jet-driven model, we estimate the density in the underlying jet to be at least 10(5) cm(-3). The outflow appears much more compact and in a different orientatio n than the arcminute-scale north/south flow seen in low-J transitions of CO . These observations represent the first successful operation of a supercon ductive HEB receiver on a telescope and demonstrate the importance of high- frequency submillimeter lines to the understanding of the protostellar envi ronment.